Batardeau

( Fr. ). A wall built acro a ditch or fortification, with a sluice-gate by which the height of the water in the ditch on both sides may be regulated. To prevent this wall being used as a pa age acro the ditch, it is built up to an angle at the top, and armed with iron spikes; and to render the attempt to cro still more difficult, a tower of masonry is built on it.